Macbook - Internet Connect Issues

I'm new, got a few questions...I have a Macbook with the latest OS X and firmware. Recently my internet has not been working (the wireless). It says I am connected and everything, but displays "problem loading page" every time. I use Firefox if that makes a difference (Safari doesn't work either though). The internet does not work in places it used to, so I know it is a new problem. When I go to Network Diagnostics, the first three are green, but the 4th (ISP I believe..?) goes back and forth, but stalls eventually.

I had a similar issue it would connect but the websites wont load. Do what i did, in my cases there was nothing wrong with my Macbook or my desk top computer(also didnt want to load the websites).
Disconnect the power(I mean pull the power cord out not only turn off by pressing the on/off button) from both your main router and the wireless router for 15 to 20 secounds then reconnect and wait for all the lights on your routers to come on(they will come on one at a time). Once they are all on open a website and see if it works. It worked for me.